1. Field of the Invention
The present invention relates to a method for controlling condensate formation in an engine system, and more particularly to a method for preventing exhaust gas recirculation when conditions conducive to condensate formation are detected.
2. Background Art
Condensation is a problem associated with engine systems using exhaust gas recirculation (EGR). Engine systems employing EGR return a limited amount of engine exhaust gas to an intake manifold to combust any unused fuel and/or byproducts present in the exhaust gas. The exhaust gas is combined with fresh air provided to the engine system. The exhaust gas and/or fresh intake air may contain water vapor. Condensation may occur when hot exhaust gas is mixed with the cooler fresh air. The resulting condensate may be caustic due to the presence of compounds of nitrogen and sulfur from fuel. For example, sulphur in diesel fuel can combine with water vapor to form sulfuric acid (H2SO4). Caustic condensate can be harmful to engine system components. Therefore, it is desirable to reduce or prevent the formation of condensate in the engine system. In particular, it is desirable to stop the flow of exhaust gas back to the intake manifold when condensate is likely to form.
Prior methods for controlling condensation did not accurately predict when condensate was likely to form. As a result, these methods disabled exhaust gas recirculation unnecessarily. Moreover, prior methods did not use actual humidity measurements, such as those provided by a humidity sensor.
It is desirable to provide a method for accurately predicting when condensate is likely to form in an engine system. It is also desirable to use a humidity sensor to more accurately predict when condensate is likely to form. Furthermore, it is desirable to locate the humidity sensor where it is not subjected to extreme environmental stresses so that a cost effective sensor may be used. Problems associated with the prior art as noted above and other problems are addressed by applicant's invention as summarized below.